diff --git a/clang-tools-extra/clangd/Selection.cpp b/clang-tools-extra/clangd/Selection.cpp
--- a/clang-tools-extra/clangd/Selection.cpp
+++ b/clang-tools-extra/clangd/Selection.cpp
@@ -224,6 +224,11 @@
     for (const syntax::Token *T = SelFirst; T < SelLimit; ++T) {
       if (shouldIgnore(*T))
         continue;
+      // Ignore tokens in disabled preprocessor sections.
+      if (Buf.expandedTokens(SM.getMacroArgExpandedLocation(T->location()))
+              .empty() &&
+          !Buf.expansionStartingAt(T))
+        continue;
       SpelledTokens.emplace_back();
       Tok &S = SpelledTokens.back();
       S.Offset = SM.getFileOffset(T->location());
diff --git a/clang-tools-extra/clangd/unittests/SelectionTests.cpp b/clang-tools-extra/clangd/unittests/SelectionTests.cpp
--- a/clang-tools-extra/clangd/unittests/SelectionTests.cpp
+++ b/clang-tools-extra/clangd/unittests/SelectionTests.cpp
@@ -521,6 +521,7 @@
   EXPECT_THAT(AST.getDiagnostics(), ::testing::IsEmpty());
   auto T = makeSelectionTree(Case, AST);
 
+  ASSERT_NE(T.commonAncestor(), nullptr);
   EXPECT_EQ("BreakStmt", T.commonAncestor()->kind());
   EXPECT_EQ("WhileStmt", T.commonAncestor()->Parent->kind());
 }
@@ -538,7 +539,7 @@
   auto AST = TU.build();
   auto T = makeSelectionTree(Case, AST);
 
-  EXPECT_EQ("WhileStmt", T.commonAncestor()->kind());
+  EXPECT_EQ(T.commonAncestor(), nullptr);
 }
 
 TEST(SelectionTest, MacroArgExpansion) {
@@ -552,6 +553,7 @@
   Annotations Test(Case);
   auto AST = TestTU::withCode(Test.code()).build();
   auto T = makeSelectionTree(Case, AST);
+  ASSERT_NE(T.commonAncestor(), nullptr);
   EXPECT_EQ("IntegerLiteral", T.commonAncestor()->kind());
   EXPECT_TRUE(T.commonAncestor()->Selected);
 
@@ -566,6 +568,7 @@
   AST = TestTU::withCode(Test.code()).build();
   T = makeSelectionTree(Case, AST);
 
+  ASSERT_NE(T.commonAncestor(), nullptr);
   EXPECT_EQ("IntegerLiteral", T.commonAncestor()->kind());
 }
 
@@ -580,6 +583,7 @@
 
   const SelectionTree::Node *Str = T.commonAncestor();
   EXPECT_EQ("StringLiteral", nodeKind(Str)) << "Implicit selected?";
+  ASSERT_NE(Str, nullptr);
   EXPECT_EQ("ImplicitCastExpr", nodeKind(Str->Parent));
   EXPECT_EQ("CXXConstructExpr", nodeKind(Str->Parent->Parent));
   EXPECT_EQ(Str, &Str->Parent->Parent->ignoreImplicit())
@@ -643,6 +647,32 @@
   EXPECT_EQ(1u, Seen) << "one tree for nontrivial selection";
 }
 
+TEST(SelectionTest, DisabledPreprocessor) {
+  const char *Case = R"cpp(
+    namespace ns {
+    #define FOO B^AR
+    }
+  )cpp";
+  Annotations Test(Case);
+  auto TU = TestTU::withCode(Test.code());
+  auto AST = TU.build();
+  auto T = makeSelectionTree(Case, AST);
+  EXPECT_EQ(T.commonAncestor(), nullptr);
+
+  Case = R"cpp(
+    namespace ns {
+    #if 0
+    void fu^nc();
+    #endif
+    }
+  )cpp";
+  Test = Annotations(Case);
+  TU = TestTU::withCode(Test.code());
+  AST = TU.build();
+  T = makeSelectionTree(Case, AST);
+  EXPECT_EQ(T.commonAncestor(), nullptr);
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang